The invention relates to a process for the continuous analysis of the composition of gases, by means of a measuring head which is used for determining the flow rate of the gases to be measured as a function of time, while the composition is analyzed using analysis equipment which is placed a distance away from the measuring head and is connected thereto by a sample line through which gas is drawn using a suction pump.
If one wishes to analyze the composition of gases in a way when such composition does not change much over time, or if one is interested only in the average composition, position can fluctuate greatly and one wishes to follow that fluctuation with great accuracy, and particularly where one also wishes to find a correlation with the flow rate of the gases to be measured, a problem is caused by the fact that the measurement of the flow rate takes place immediately, whereas and the measurement of the concentrations is delayed in time due to the distance of the analysis equipment from the measuring head. In order to correct this time difference, the procedure hitherto has been to feed in by hand, using a balloon, a quantity of a suitable calibration gas in or near the suction aperture of the sample line at the measuring head, and then to determine from the observed time of entry of said calibration gas into the analysis equipment the time required for the flow the gas through the sample line from the measuring head to the analysis equipment. This time will hereinafter be referred to as the "transit time". This calibration is, however, not accurate, on the one hand because the time of delivery of a quantity of calibration gas by hand cannot be determined accurately, or cannot be correlated accurately with the reading in the analysis equipment and, on the other hand, because the transit time is not a constant. In fact, said transit time depends on all kinds of environmental conditions, the temperature being the main factor, but the atmospheric pressure and, for example, the moisture content of the gas to be analyzed also playing a role. Carrying out measurements on gases with variations in the composition with a period of 2 to 3 seconds was therefore so inaccurate that it can be said that such measurements were hitherto impossible.